1. Field of the Invention
The present invention relates to systems for preventing the stagnation of fluids stored in large reservoirs.
2. Description of the Prior Art
Fluid reservoirs, particularly those used to store potable water, have historically had to contend with stagnation problems. Stagnation in such conventional potable water reservoir systems is a function of the size of the reservoir and, in particular, the relative dimensions of the cross-sectional area of the reservoir in plan view coupled with the number and location of inlet and outlet pipes. Conventional reservoirs are typically filled and drained from a single pipe located at one end of the reservoir. Filling and draining fluids through such a single pipe or conduit creates very little turbulence, particularly in areas within the reservoir remote from the inlet/outlet conduit.
In potable water reservoirs, water may not mix or be “turned over” in those areas remote from the inlet/outlet conduit. This is referred to as stagnant water. Potable water is typically “chlorinated” through the addition of hypochlorite or “chlorine” as a disinfectant to prevent microbial growth in the water. The chlorine concentration will decrease in stagnant water over time, resulting in unsanitary water quality if a sufficient degree of mixing between influent water and reservoir water is not maintained.
To a large extent, the fluid added to a reservoir through a single inlet/outlet conduit remains near the single pipe and is removed first during drainage operations, while the fluid previously in the reservoir remains. This phenomenon is generally referred to as “short-circuiting.” Short-circuiting is the continual recirculation of the freshest water near the inlet/outlet conduit. Water outside of this area of influence becomes stagnant and loses disinfectant residual.
The prior art recognizes that the use of a plurality of inlet and outlet pipes would increase the mixing of fluids stored in reservoirs. However, the retrofitting of existing reservoirs to include additional inlet and outlet conduits can be quite expensive. The prior art also recognizes the use of reservoirs having a circular cross-section in plan view in an attempt to increase fluid mixing and eliminate “dead zones” that typically occur in the remote corners of reservoirs having rectangular cross-sections. However, fluid stagnation problems can still exist even if these improvements are deployed in conventional reservoir systems.
U.S. Pat. No. 6,016,839 to Raftis et al. discloses an air diffuser system for use in wastewater treatment that includes a manifold and a plurality of elastomeric “duckbill” check valves. The purpose of the air diffuser system is to inject and diffuse one process fluid into another process fluid for the purpose of aeration, diffusion, agitation, or mixing. The system is particularly well suited for activated sludge applications. However, the system does not employ duckbill check valves oriented to allow fluid to drain from the reservoir into the same manifold and inlet conduit by which it entered. Moreover, the Raftis et al. patent specifically discloses the benefits of using such “duckbill” check valves to prevent fluids stored within a reservoir from reaching the manifold.
There remains a need for an apparatus to minimize or eliminate short-circuiting, “dead zones,” and/or stagnant areas in large, fluid-containing reservoirs, especially where the reservoirs contain potable water.